backbreaking vs gruelling

backbreaking and gruelling both are adjectives.

Word	Noun	Adjective	Verb	Adverb
backbreaking	No	Yes	No	No
gruelling	No	Yes	No	No

As adjectives, backbreaking and gruelling are synonyms defined as:

backbreaking and gruelling: characterized by effort to the point of exhaustion; especially physical effort

Other synonyms of backbreaking include arduous, grueling, hard, heavy, laborious, operose, punishing, toilsome.

backbreaking (adjective)	gruelling (adjective)
characterized by effort to the point of exhaustion; especially physical effort	characterized by effort to the point of exhaustion; especially physical effort